This invention relates to an endoscopic foreign body retrieving tool that is passed through a treatment tool insertion channel in an endoscope to retrieve foreign body and the like from within body cavities.
Endoscopic foreign body retrieving tools are generally designed to retrieve foreign body and the like by grasping them with a plurality of arms that xe2x80x9cpinchxe2x80x9d them from the outside. However, foreign body such as an artificial tooth crown is so slippery that it cannot be held stable after being grasped by the pinching action. To deal with this problem, the present inventor previously filed a patent application on an invention of an endoscopic foreign body retrieving tool having a plurality of foreign body catching arms that would function by spreading outwardly (Unexamined Published Japanese Patent Application No. 346993/1999).
While various types of endoscopic foreign body retrieving tool are disclosed in Unexamined Published Japanese Patent Application No. 346993/1999, they are classified in two major categories, one being such that a manipulating wire is pushed forward to drive a link mechanism at the tip to spread foreign body catching arms and the other being such that elastic foreign body catching arms will spread by themselves when pushed out of a sheath. However, endoscopic foreign body retrieving tools in both categories have their own problems. In order to ensure that foreign body is securely held by the spread catch arms, the manipulating wire of the retrieval tool in the first category has to be kept pushed in by the operator and if he slackens it by the slightest degree while he is retrieving the foreign body, he may drop it. In the retrieval tool of the second category, the catch arms typically formed of elastic wires will spread by themselves and the resulting spring force is the only power that is active to hold foreign body and it is sometimes insufficient to prevent the foreign body from dropping.
An object, therefore, of the invention is to provide an endoscopic foreign body retrieving tool that is so designed that a plurality of foreign body catching arms function by spreading outward and which still features high retention performance, sustaining adequate force to retain foreign body.
This object can be attained by an endoscopic foreign body retrieving tool comprising a flexible sheath, a manipulating wire provided within the flexible sheath to be capable of moving back and forth through it along the longitudinal axis and a plurality of foreign body catching arms made of an elastic material and connected to the distal end of the manipulating wire such that they spread in a free state by their own elasticity when they are outside the sheath whereas they contract if they are drawn into the sheath, characterized in that each of the foreign body catching arms has an intermediate curved portion formed midway which, upon contact with the inner peripheral surface of the sheath, undergoes elastic deformation such that the distal end portions of the foreign body catching arms are forced to spread wider than when they are in the free state.
The intermediate curved portion may draw a smooth curve which is outwardly convex when the foreign body catching arms have spread in the free state. If desired, the part of each foreign body catching arm that is beyond the intermediate curved portion toward the distal end may be oriented parallel to the longitudinal axis of the sheath when the foreign body catching arms have spread in the free state.
The distal end portion of each foreign body catching arm may be bent outward. If desired, the foreign body catching arms may be so adapted that they are entirely drawn into the sheath up to the distal end portions by pulling the manipulating wire toward the basal end.
The present disclosure relates to the subject matter contained in Japanese patent application No. 2000-66043 (filed on Mar. 10, 2000), which is expressly incorporated herein by reference in its entirety.